There was another mass shooting that happened not too long ago, and after the horror that was the Vegas tragedy, I do think that something needs to be done. I don't think that it's possible to prevent all of this, and I think that we'll always have gun violence and some mass shootings. BUT, there are ways to decrease this.
When Hillary was running (Her second time.) against Bernie, she came up with this ABSURD idea to sue the gun manufacturers and the dealers, and to hold them responsible for gun violence and mass shootings (This was in response to a lawsuit that was filed by the families of Sandy Hook victims.). It is really absurd (I mean, you don't go after Budweiser for Drunk Driving deaths, or Honda for vehicular manslaughter, do you?), but it might actually have some merit. Maybe if guns were better regulated or harder to obtain legally, this stuff wouldn't happen. I don't know, but I'm actually starting to kind of see her point. It's not going to happen anytime soon, but maybe we do need some more gun laws.

...and the pharmaceutical companies that kill far more every year would make a better target imo.